Hello,
today I installed K70 RGB and had problems with boot up delay and keyboard not working after start (could not enter bios), so I restarted and booted directly to bios, when I changed the polling rate, keyboard started working in bios and did not stop regardless of switch position. I changed USB initialization from partial to full and now everything is okay.
I have keyboard plugged into USB 3.0 port.
My HW can be found in my profile details and I am using latest available bios, drivers and keyobard firmware (1.20).
UPDATE: I also had to disable Intel xHCI.
UPDATE2: Ok, at the end it seems, that whole problem was with Intel xHCI so I disabled it completely and even changed usb initialization back to partial and now the boot time is ok, keyboard is working all the time and keyboard is not slowed down until all startup things in windows are loaded up.
UPDATE3: I had to turn on the Intel xHCI, because my DAC connected through USB didn't work properly (same problem occured with USB 2.0 and USB 3.0). And now keyboard sometimes works ok at start and sometimes boot time is longer and keyboard looks dead during bios load time.